Progressive drying kiln



Feb. 16, J, F COBB PRohREssIvE DRYING KILN Filed Dec. 5, 1.925 aSheets-Shet 1 W 0 K m J", L

Feb. 16, 1932. J, F. coBB PROGRESSIVE DRYING KILN Filed Dec. 5, 1925 6Sheets-Sheet 2 gwuantm;

m N R E Feb. 16, 1932. J, 3055 1,845,398

PROGRESSIVE DRYING KILN Filed Dec. 5, 1925 6 Sheets-Sheet 5 55 i I 000 Aoo I\" i W 1 i I 2 v Z v 1 1 I, v l w?! R Y/ Feb. 16, 1932.

.1. F. cosa 1,845,398

PROGRESSIVE DRYING KILN Filed Dec. 5, 1925 6 Sheets-Sheet 4 Feb 16,1932. J. F. COBB PROGRESSIVE DRYING KILN 6 Sheets-Sheet 6 Filed Dec. 51925 gwuento'z;

Patented Feb lid, 1932 I I E PATET 3'. FORREST COBB, OF PORTLAND,OREGON, ASSIGNOB TO MOORE DRY KILN' COMPANY, A CORPORATION OF FLORIDAPROGRESSIVE DRYING KILN Application filed December 5, 1925. Serial No.2'83504.

My present invention relates to apparatus low a generally descendingcourse at the infor drying organic substances and part1cutake end of thekiln where the weight of larly but not exclusively for drying lumber.Water or aqueous substance is greatest and Selected for enumeration fromamong nuwhen it has strong tendency to descend by merous objects of myinvention, those set gravity towards the floor of the kiln, and to 55forth in the next following general statecause it to follow an ascendingcourse as the ment are at present deemed most important. stockapproaches the outlet end of the kiln,

In general terms the main object of my where the heated and dried mediumassumes, invention is to provide means for increasing by reason of itsbuoyancy, a rising tendency, the speed and uniformity of the dryingoperdue to well known physical laws. 60 ation of a kiln. In theforegoing description contained in A scarcely less important object ofmy 1n the preceding paragraph, the use of vertical vention is to providein a kiln through which piling lumber or of a vertical flue system ofthe stock to be dried is Caused to advance piling is contemplated; butit should be un- 35 from end to end by progressive step by st p derstoodthat the same principle applies if a movements, means for causing theclrc lahorizontal or other form of piling is emtion within the kiln of agaseous drymg 111B- ployed, the only diiference being that in the diumhaving a gradually increasing temp r latter instance the circulatorymedium is ture beginning with a comparatively l0W deforced underpregsurg to pass through the 20 gree of heat at the intake end of thekiln, a transverse interstices the pile of lumber g lncreasing to amaximum hlgh degree at the i order. t reach a Space th h hi h it outletend thereof. may ultimately accomplish a substantially The purpose ofthe object just Set forth vertical descent or ascent, as the directionof is to apply a circulating med m at a 10W its circulation at difierentpoints of circula- 25 degree of heat and high percentage of h1}- tion,respectively, may demand. 7, midity to the stock when in a'green state1t The means for attaining the object menfilSlZ QIItGIS the kiln andwhen it is most heavtioned in the second above paragraph may ily ladenwith moisture required to be gr operate through the, sole agency of heata ually removed from it in the drying p plied within the kiln, orthrough the add i n: afterwards as the molstllle 15 tional agency of aforced draft obtained in 30 eliminated from the stock by evapq tomechanical means. In the following speciti pp y ultimately to the StockSal-d cllclllatlng cation I illustrate and describe separately themedium substantially dehydrated and at a t means pfopgsed t b emplgyed di high degree of heat at a. stage of the dry g respect to means forproducing a forced draft process when such applica on may b made I alsoillustrate and describe two distinct as not only without injury but withpositive adtypes f mechanism f accomplishing th vantage to the qualityof the product resultb t proposed, ing fr m the C0m1918te y g operatlon-B? In addition to the main objects above spectween the two extremes of ht Mid humldl' ified, my invention comprehends numerous w fication abovespecifi d th 15 Of course details of construction andfcombination of cograduation o COMlitiOBS p y and mechanical elements which it is deemedundownwardly toward said eX r m necessary to further indicate in thisgeneral Another Object is to Provide PQSltWe one statement, in view ofthe detailed specifica- Way circulation through the stock, in difiertihi h f ll t 4.5 ent directions in the two ends of the kiln. Wh t tit t yi ti will be, to

Another object of my invention is to prohereinafter described in detailand afterride means for effecting within the kiln re- Wards succinctlydefined in the appended versal of the direction of circulation of theclaims. circulatory medium, said means being pref- In the accompanyingdrawlngs, wherein erably devised to cause said medium to fol arrows areused wherever it is deemed nec- 1 essary to indicate the direction ofmovement,

Figure I is a longitudinal section of a kiln embodying that form of myinvention in which heat alone carried in steam coils is depended upon asa means of effecting circulation within the kiln of a gaseous dryingmedium. I

Figure II is a top plan view of the system of heating coils shown inFigure I.

Figure III is a view of a kiln similar to that in Figure II, showing inplan a power fan for effecting gaseous contents of the kiln by'aid of atwoway circulator, the heating coils as shown in the receding figuresbeing omitted for the sakeo sim lifying the drawings.

Figure I 7 is a longitudinal section of the kiln shown in Figure III,showing the de tails of the fan mechanism in full lines and the heatingcoils in dotted lines.

Figure V is a vertical transverse section, on the line V-V, at the inletend of Figure IV, this illustration minus the circulator being alsosubstantially applicable to Figures I and II. 1

Figure VI is a vertical transverse section to like effect in respect toFigures I and II, as Figure V, but taken on line VI-VI of Figure IV, atthe outlet end of the kilnshown therein.

Figure VII is a view similar to Figure I, but showing heating fluescommunicating with a furnace as a modification of the heating meansrepresented by the steam 60115 In Figure I.

Figure VIII shows a further modification of a forced draft system, inwhich internal fans operatively disposed along a rotatable shaft withinthe kiln are shown in combination with heating flues as shown in FigureVII, but being equally a plicable,'upon sub which some parts arestitution of steam coils or flues, to the system of heating by steamcoils as shown in Figures I and II.

Figure IX is a vertical transverse section on the line IX-IX of FigureVIII, at the outlet end of the kiln.

Figure X is an elevation of the outlet end of the kiln shown in FiguresVIII and IX.

Figure XI is a vertical longitudinal section of portions of my kiln inthe form shown in Figure VIII made to illustrate in side elevation theconstruction of one side wall of the fan enclosure shown in said figure,of

omitted.

Figure XII is a horizontal longitudinal section of the subject matter ofFigure XI, made to illustrate in top plan view complete the fanenclosure of the preceding figure.

Referring to the numerals on the drawings, 1 indicates a kiln chamberwhich may be a substantially air tight structure of any desired size anddimensions, and built in any preferred manner of any suitable material.

- The chamber 1 is usually an oblong buildforced circulation of the1,e45,sas

ing having suitable doors at its opposite ends for inlet and outletrespectively of stock to be dried. Of such doors, two, for example only,of the vertically movable sort are indicated by numerals 2 and 3, inFigures VII and VIII.

The chamber 1 is preferably traversable from end to end by truck loadsof any material to be dried which is herein designated generally by theterm stock, the-same bemg preferably carried on tracks 4 which may be asingle track or a plurality of tracks as may be desirable, providedsubstantially in the 'usual and well known manner. The tracks 4 arereferably supported near the middle altitu e of the chamber 1, as by I-beams 5 supported in the side walls of the chamber which is alsoprovided with the usual equipment including ventilators of any preferredtype.

Doors 6 for admission of fresh outside air, if desired, may be providedat opposite ends of the chamber 1 as shown for example, in

Figures VII and VIII.

A kiln chamber with its appurtenances, such as I have just described,for example, is already well known in the art, and is referred to onlyin sufficient detail to meet the requirements which the subsequentdescription of my invention demands.

A feature common to all forms of embodiment of my invention is found inthe provision of means for effecting within different parts of a kilnchamber 0 currents of circulation. uch means may, for example, comprisea cumulative heating system, that is to say, a system for heating theinterior of the chamber 1 in which the effective heating capacity of thesystem is, as by multiplication at one end of the kiln of the heatingelements, for example, the steam coils, regulated and controlled.

For'instance, in Figures I and II, coils of steampipes 7 are keptsupplied as through headers 8 with an adequate supply of steam derivedfrom a source not illustrated.

The pipe coils may extend, substantially I but not quite, from end toend of the chamber 1. At its end into which stock to be dried is firstintroduced, which is next the headers 8 and which is called the inletend, the coils are reduced in heating capacity by reduction of theirheating surface to that of a single layer of pipes or, if desired, tocurtailment positely directed The said load, progressing with step bystep movement through the kiln finds a gradual rise of temperature andlowering of humidity until the temperature reaches maximum and thehumidity minimum just before the final discharge of the stock, load byload, from the kiln.

Instead of the steam coils 7, other heating agency may be employed. Forexample, in Figure VII a system of direct heating fiues 9, leadingpreferably underneath the track rails 4 from a furnace 11 to a stack 12,is substituted, with similar effect but with desirable economy in someinstances, for the steam coils 7. It'is contemplated that interchange ofone heating system for another, in all the various forms of embodimentof my invention, may be effected at will according to variations ofconditions which are present in the actual drying operation.

In all forms of embodiment of my invention, some means for efiectingcirculation of the circulatory medium, that is to say the gas eouscontents of the chamber 1, must be employed. In the embodiment shown inFigures I and II, the means contemplated for effecting suchcirculationis heat alone, which operates by imparting superior. buoyancy to oneportion of the contents of the chamber over the remainder thereof and atthe same time effects a positive down-draft by pull upon the body of thecirculatory medium due to the tendency of a portion of said medium tofall by gravity. The desired circulation obtained by heat alone may befurthermore aided by at least two means. One of such means for aidingcirculation is derived from the employment of two sets of baffles 14 and15, respectively, disposed towards opposite ends of the chamber 1. Thebafiies 14 preferably consist of vertical plates disposed between thelegs of the system of steam coils 7 which is bifurcated for theiraccommodation at the inlet end of the chamber 1. At the opposite endthereof the fork 16 of the bifurcation of the said system is located,and also the heat-. ing efficiency of the system is amplified, in themanner already specified, to its full cumulative capacity. Towards theend last mentioned of the chamber 1, the bafiies 15 are located and aredistinguished from the baflles 14 by being located so as to flank thepipes of the heating system upon its opposite sides.

It is to be understood that employment of the bafiles 14 and 15 isoptional, and only that under some conditions their use is advantageousand therefore preferable. If without the battles the bifurcated heatingsystem is used, represented by steam coils 7 havin the fork 16 fromwhich the two legs of the cating system extend, a degree of circulationis obtained, the function of'the bifurcated system in such instancebeing to distribute the eifective heat at the forked end of the systemmedially within the kiln chamber and the effective heat at the twolegged ends of the system to the sides of the kiln chamber. The result,in such case, is to effect a circulation of the circulatory medium fromthe middle of the kiln chamber to the sides thereof or from the sides tomiddle of the kiln chamber as may be desired. The result, as aforesaid,is to produce the transverse circulation else where herein specified,said circulation being upwardly directed in the middle and down thesides of the kiln chamber at its outlet end or, in other words, thenarrow end of the heating system, for example the end in which the fork16 is located. At the same time the circulation at the two legged end ofthe heating system, namely the end opposite the fork 16, takes place upthe sides and down the middle of the kiln chamber, that is to say, in areverse direction from that proceeding at the end of the system wherethe fork 16 is located.

The height of the bafiles 14 and 15 may be variedin sound discretion,the purpose of them being to prevent short circuiting' of the currentsof the circulatory medium, or, in other words, positively to compelsaidmedium to pass through the spaces between the heating coils and throughthe interstices of the stock to be dried. To that end said bafflesshould extend both above and below the tracks .4 a sufiicient distanceto obstruct the open spaces'thereabout and to prevent the circulatorymedium from following a line of least resistance which the absence ofsuch obstruction might present.

The second means above noted for aiding natural circulation may consistof spraying devices disposed wherever desired for obtaining the resultof aiding the circulation. By spraying devices I intend to include steamjets, water sprays or sheets, and air blasts.

A third means for aiding natural circulation may consist, as elsewhereherein specified, of multiplication of the area of the heating surfacesemployed, for example by accumulation of steam ipes in larger or smallergroups at points esired.

In operation, the circulatory medium within the kiln is caused even by acomparatively low temperature, to ascend 'by reason of its rarefaction,through the portions of the coils 7 that are located in passage waysdefined by the bafiies themselves outside the bafiles 14. Thence thecurrent of'circulation enters and ultimately descends through the stockloads on the tracks 4 carrying with it from the stock moisture ofevaporation therefrom, which has in itself, by reason only of itssuperior gravity, a definite tendency to descend. In

this manner a transverse circulation of the contents of the kiln is keptup about each stock load, with a tendency to penetrate interstices inthe load wherever they are provided. 1

While this is going on at one end of the chamber 1, a reversecirculation, in consequence of the relative disposition of the bafflesin respect to the stock load or loads adja cent to them is taking placeat the other end of the chamber 1.

At some variably disposed vertical plane along the longitudinal axis ofthe chamber, the two oppositely rotatory currents must meet. Thelocation of said plane ma be varied at will with effect of ultimate gainin the final results of its drying operation.

There is, moreover, a longitudinal circulation from end to end of thechamber 1 taking place within it at all times while the kiln is inoperation. This results from a prepon derance of air pressure at theoutlet end,

whereby an accumulation under pressure of the circulating medium at thetop of the outlet end of the kiln is compelled by said pressure to seekegress by descent through the stock at the inlet end of the chamber. Theresult efiected is a circulation of the circulatory medium in twodirections, with a consequent commingling at each end of the kilnchamber 1 of portions of the said medium derived from the circulationwhich is constantly taking place at opposite ends of the kiln chamber.One of said commingling portions is derived from the transversecirculation induced by the operation of the baflies 14, where thecirculatory medium 'is heavily laden with the moisture of evaporationfrom green stock. The other portion of the circulatory medium is derivedfrom the outlet end of the kiln chamber and where it is keptconsequently in a comparatively hot and dry state. The combined effectof the twofold currents of circulation just described is to temper,advantageously to the product of the kiln, the condition of thecirculatory medium at each end of the kiln chamber by contributions toit of portions of said medium drawn initially from the opposite ends ofsaid chamber under contrasting conditions which there exist, butgradually changing in quality of heat and moisture as it moves fromeither end of the chamber to the other.

It may now be observed that instead of depending upon the operation ofheat alone as the means for effecting circulation of the circulatorymedium within the kiln. chamber, mechanical means, ancillary to themeans first mentioned, may be often used to advantage.

Such ancillary mechanical means is shown in two difi'erent forms inFigures III-VI and in Figures VIII*X, respectively.

In the group of figures first named in the last preceding sentence, theancillary mechanical means comprises what may be denominated acirculator in operative communication with a power-driven fan 20. Thefan makes delivery through a main duct 21 to the circulator, andpreferably makes upon return ducts 22 and 23 of the circulator. The fanis preferably located outside of the kiln chamber 1, while all the ductsare in operative communication with the interior of-said chamber asthrough suitable delivery ports 24 and intake ports 25, respectively,disposed at suitable intervals along the respective duct-s.

At about the middle of the kiln chamber 1, the main delivery duct 21 isbifurcated into two branch delivery ducts 26 and 27, so that While themain delivery duct is disposed throughout its length medially within thechamber 1, the branches are disposed likewise alon the opposite sidesthereof, as illustrated in Figure III.

As shown also in Figure III, the return ducts 22 and 23 are unifiedsubstantially in mid chamber into a single return duct 28 which isdisposed medially within the kiln chamber 1. By aid of the circulatorthrough theoperation of the fan 20, the circulatory medium is, at theintake end of the kiln, driven upwardly from the branch delivery ducts26 and 27 upon opposite sides of the bafiles 14:, and is, aftereffecting transverse circulation in the manner already described withreference to Figures I and II, sucked into the single return duct 28.Simultaneously with the operation described in the last sentence themain delivery duct 21 is making delivery to the interior of the kilnchamber 1 at its outletend so as to create a transverse current ofcirculation returning to the fan through induction by suction into thereturn ducts 22 and 23, respectively. It should be observed that thecirculator above described is, in operation, strictly ancillary to themeans of circulation described with reference to Figures 1 and H, andthat its operation is attended with the same 'longitudinal circulationas that described with reference to said fi 'ures, but only to anincreased or amplified degree or extent.

By proper selection of the type of fan 20 employed, and by adaptation ofthe fan to the purpose required of it, the said fan may be madereversible, so as to reverse the direction of rotation of thecirculatory medium at the opposite ends of the chamber, wheneverdesired. By such reversibility of the direction of rotation of thecirculatory medium a peculiar uniformity of the drying operation uponthe drying stock may be effected.

The ancillary mechanical means of circulation shown in Figures VIII-X,comprises an internalfan mechanism, consisting of a rotatable shaft 30,which is operatively mounted on upright bearing-supports 31 within andalong the length of the kiln chamber 1, and of disc fans 32 and 33 fixedto said shaft at intervals alon its length. The fans 32 make airdelivery in one direction and the fans 33 in the opposite direction,with the result of a reversal of direction of circulation substantiallyto the same effect as the circulatory operation described with referenceto Figures III-VI. The area immediately about the fans 32 and 33 is, asshown in Figures XI and XII, flanked by side walls 35 and 36 extendingsubstantially from end to end of the interior of the chamber 1, whiletransverse upright plates or partitions 38 are disposed at intervalsdetermined by the location of the respective fans along the length ofthe shaft 3O. The partitions 38 are secured to the opposite side walls35 and 36 and rising substantially to a plane tangential to the tops ofthe several fans extend outside the walls 35 and 36 in wing baffies 39which partially fill the spaces between the said walls and the innersurface of the outside wall of the kiln with deflecting effect upon thecirculatory medium. These wing baffles 39 are adjustable by the commonexpedient of permanent fiexure and remain set in adjustment imparted tothem. A medial partition 40 identical in form to the partitions 38divides the space between the walls 35 and 36 into two lengths (notnecessarily of equal extent) in one of which rotate the fans 32 and inthe other the fans 33. Bafile plates 41 depending from a suitablesupport below the tracks 4 are disposed at intervals in opposition eachto its respective fan so as to co-operate each with its correspondingpartition with the effect of directing upwardly into the interior ofkiln chamber 1 at one end the current of air derived from the rotationof each fan. The shaft 30 is driven by any suitable means as, forexample, a belt 42 passing about pulleys 43 and 44 upon said shaft andthe shaft of an electric motor 45, respectively.

The walls 35 and 36 extend upwardly in vertically inclined plates 47 and48, respectively, which define between them, for their full length, anopen throat 49. Between next adjacent wing baflles 39 on the transversepartitions 38, the walls are at intervals broken away or provided withsuitable openings, as indicated at 50, with the following effect,namely, that the fans 32 by their rotative movement serve to suck infrom above the circulatory medium through the throat 49, and todischarge it laterally through the openings 50 whence it is caused tocirculate transversely through the interior of the kiln, returning insaid circulation through the throat 49 as aforesaid, but not necessarilyreturning to the same fan as that from which it first proceeded.

The fans 33, encased precisely as are the fans 32 and rotated with them,suck in the circulatory medium through the openings 50 and dischargethem u wardly through the throat 49. It will there ore appear that thereis effected a reversal of the direction of trans verse circulation atopposite ends of the chamber 1 on opposite sides of the medial partition40. It will also appear from what is already specified that alongitudinal circulation takes place within said chamber ofthe'circulatory medium derived from that which enters into thetransverse circulations which I have just above described.

The same effect in respect to reversal of circulation may beaccomplished by using fans, 32 and 33, respectively, of the kindcommonly known in the art as right hand and left hand fans, disposed onthe opposite sides of the medial partition 40, the duct systemcomprising the members 35, 36, 37, 38, 39, 40, 47, 48, 49, and 50, aspreviously specified being retained.

t should be observed that the internal. fan mechanism last described isshown as combined with a flue heating system, but it should be in thatconnection borne in mind that each heating system contemplated by me is,as already specified, regarded by me as interchangeable in everyinstance with another.

In addition to what has been already specified, it should be mentionedthat it is my purpose to provide within the kiln chamber 1 hot fluiddelivery pipes 55 distributed at such points as may be deemed mostadvantageous. Such pipes may be, at wise discretion, made to dischargesteam, water, or-air in fine jets or sheets for purposes well understoodin the art, it being understood that such jets or sheets may be employedso as only, for the most part, to accelerate currents of circulation, orthey may be employed also for the purposes of humidifying or ventilatingthe circulatory medium. For the purpose of acceleration the pipes 55should discharge in. any direction which the flow of the circulatorymedium may require, or they may be adapted for reversal of direction ofdischarge to meet the requirements of reversibility of circulation wherereversibility, as has been elsewhere herein specified, may necessitate.For the purpose of simple humidification or for ventilating purposes,the pipes may make lateral discharge so that they will be neutral, and,therefore, suitable for any direction of flow of the circulatory medium.

The operation of my invention is deemed in the main, to be so plain andso sufiiciently set forth in the foregoing specification as to requireno recapitulation here, but it may be added that in utilizing my kilnfor drying of lumber for instance, no special method of piling orstacking the lumber on the trucks need be employed. Each of piling asnow known in the art or as may be devised may have, under certainconditions, special advantages, but my kiln, in its various forms andmethods of o eration, is deemed to be advanta eously a aptable to allavailable methods 0 piling lumber which may be employed in the art ofkiln drying.

What I claim is:

particular method of said circulator movements, respectively. 23in a'dring iln,the combination with .a kiln cham r,.and stock-supporting track:there'infof heatingmeans in operative relato' stock'su'pported on saidtrack, said means comprising means for eflecting at each end ofithe kilnchamber a separately directed circulative movement of the aseous mediumof circulation relatively to tie stock in the kilncha'mber, meansancillary to said heatingmeans for compelling said circiilativemovements, respectively, and means for effectingadditional circulationof said circulatory' medium from end to end of the kiln chamber.

3. In a drying kiln, the combination with a kiln chamber,stock-supporting track therein, heating means therefor comprising,substantially at opposite ends or" the kiln chamber, areas of heatingsurfaces of different capacities, means for efiecting transversecirculation of the gaseous medium of the chamber heated'by saidsurfaces, respectively, in difierent directions relatively to the stockload, whereby, the relative capacities of the said heating areas'is madeto effect of t e heating medium within the kiln cham ber. In a dryingkiln, the combination with a kiln chamber, and stock supporting tracktherein, or a driven shaft rotatable within the chamber, fans fixedat-intervals upon said shaftlto rotate with it, and plates in effectpartially encasing each fan and defining openings for circulation of agaseous circulatory medium relatively to each fan, whereby each 'faneffects anindividual circulation within the chamber, some of said fansoper-.

ating upon said circulatory medium by suction from the chamber andothers by propulsion thereinto, whereby predetermined currents inopposite directions are set up and maintained within the chamber.

"5. In a drying kiln, the combination with a kiln chamber, and stocksupporting track therein,jof a driven shaft rotatable within thechamber, fans fixed at intervals upon said shaft to rotatewith it, andplates in effect partially encasing each fan and defining openings forcirculation of a gaseous circulatory medium relatively to each fan,whereby each fan eflects an individual circulation longitudinal as wellas transverse circulation within the chamber, some of said fansoperating upon said circulatory medium by suction from the chamber andothers by propulsion thereinto, whereby predetermined currents in oposite directions are set up and maintaine' within the chamber, andmeans for reversing the direction of the shaft whereby the fans may bemade to function with reverse effect, respectively.

6. In a drying-kiln, the combination with a kiln chamber, and stocksupportin track therein, of a driven shaft rotatable witliin thechamber, fans fixed at intervals upon said shaft to rotate with it, andplates in effect partially encasing each fan and defining openings forcirculation of a gaseous circulatory medium relatively to each fan,whereby each fan effects an individual circulation w thin the chamber,some of said fans oper atmg upon said circulatory medium by suct on fromthe chamber and others by propul- S1011 thereinto, whereby predeterminedcur-v rents in opposite directions are set iipan d maintained within thechamber, and a medial partition dividing the interor of the chamber intotwo lengths, one set of said fans being located in one of said lengthsand the other set of fans being located in the other length, wherebycirculation longitudinally within the kiln from one set of fans to theother may be effected.

7 Ina dr ing ln'ln, the combination with a kiln cham er, and stocksupportin track therein, of a driven shaft rotatable wit in the chamber,fans fixed at intervals upon said shaft to rotate with it, and plates inefiect part ally encasing each fan and defining openings for circulationof a gaseous circulatory medium relatively to each fan, whereby each faneffects an individual circulation within the chamber, some of said fansoperatmg upon said circulatory medium by suction from the chamber andothers by propulsion thereinto, whereby predetermined curents inopposite directions are set up'and maintained within the chamber, amedial partition dividmg the interior of the chamber into two lengths,one set of said fans being located in one of said lengths and the otherset of fans being located in the other length, whereby circulationlongitudinally within the kiln from one set of fans to the other may beeffected, and means for reversing the direction of rotation of the shaftwhereby the'direction ofsnovement of all the several currents ofcirculation within the kiln chamber may be simultaneously reversed atwill.

8. In a drying kiln, the combination with a kiln chamber, andstock-supporting track therein, of heating means in operativerelationship to stock supported on said track, said means comprisingmeans for effecting at each end of the kiln chamber a separatelydirected transversely circulative movement of the gaseous medium ofcirculation relatively to the stock in the kiln chamber, and spraysoperatively discharging into the body of the circulative medium andterminally disposed with respect to the chamber.

9. In a drying kiln, the combination with a kiln chamber, track railstherein, and fiat piled stacks of lumber supported on said rails, ofheating means in operative relationship to said lumber, and oppositelydirected reversible means, substantially at opposite ends of the kilnchamber, for effecting circulation through the lumber in oppositedirections at opposite ends of the kiln chamber.

10. In a progressive drying kiln, the combination with a kiln chamber,stock-support- 1ng track therein, and heating means in operativerelationship to stock supported on said track, of a circulatorcomprising supply ducts and delivery ducts, said ducts being branchedfor difierently directed discharge, respectively, at the opposite endsof the kiln, and being operatively disposed in relationship to saidheating means within the chamber, and reversible means for producingcirculation within the kiln through said ducts, respectively, wherebyreversal of the operation of the 'respective ducts may be accomplishedwlth distinctive drying effect on the stock.

1i. In a drying kiln, the combination with a kiln chamber, and stocksupporting track therein, of a driven shaft rotatable within the.chamber, partially encased fans fixed at intervals upon said shafttorotate with it, said fans at one end of the chamber being adapted tomake delivery toward one side of the chamber and those at the other endof the chamber being adapted to make delivery towards the other side ofthe chamber.

12, in a progressive kiln having truck supporting tracks therein, aunitary heating system having more heating surface at the dry end thanat the green end, said heatin systern being divided to be on oppositesides of a pair of baflles at the green end of the kiln and massedtogether at the dry end, being flanked by a pair of bafiies to producean oppositely directed circulation at the opposite end of the kiln.

13 In a progressive kiln having truck supporting tracks therein, aunitary heatingsystern having more heating surface at the dry end thanat the green end, said heating system being divided to be on oppositesides of a pair of bafiies at the green end of the kiln and massedtogether at the dry end, being flanked by a pair of bafiles to producean'oppositely directed transverse circulation at "opposite ends of'thekiln and a longitudinal circulation independent of the transverseoppositely 1directed circulation at opposite ends of the iln.

14. In a progressive drying kiln having stock supporting tracks therein,a driven shaft rotatable within the chamber, partially encased fansfixed at intervals uponsaid shaft to rotate with it, said fans at oneend of the chamber blowing through lateral banks of coils, and fans atthe opposite end sucking through a lesser number of heating coils.

15. In a progressive drying kiln having stock supporting tracks therein,a driven shaft rotatable within the chamber, partially encased fansfixed at intervals upon said shaft to rotate with it, said fans at oneend of the chamber blowing through lateral banks of coils, and fans atthe opposite end sucking through a lesser number of heating coils, saidfans being reversible.

16. In a progressive kiln, the combination with truck supporting trackstherein, of

means for producing successive currents of transverse circulationthroughout the kiln chamber, means for imparting difier'ent de grees ofheat to saidsuccessive currents o a kiln chamber, and stock-supportingtrack therein, of heating means in operative relationship to stocksupported on said track, a circulator also in operative relationship tosaid stock, said circulator having at its 9p posite ends, respectively,relatively transposed supply and return ductsso arranged as in operationto produce oppositely directed transverse circulations at each end ofthe kiln chamber, and a power driven fan in operative communication withsaid circulator.

18. In a drying kiln, the combination with a kiln chamber, andstock-supporting track therein, of heating means in operativerelationship to stock supported on said track, a

.circulator also in operative relationship to tionship to stocksupported on said track, a

circulator, substantially as specified, also in operative relationshipto said stock, said circulator having at its opposite ends, respec-"tively, relatively transposed supply and return ducts so arranged as inoperation to produce oppositely directed transverse circulations at eachend of the kiln chamber,

and a. power-driven fan in operative communication with said circulator,said fan comprising means of communicating with the supply andreturnducts,

respectively.

17. In a drying kiln, the combination with 20. A rogressive dry kilncomprising an elongatetfchamber provided with means for heatingthechamber, means for producing circulation of the air within the chamberlongitudinally through the material therein and means for producingcrosswise circulation of the airthrough the material within the chamber.21. A" progressive dry kiln comprising an elongated chamber providedwith means for V heating the air withlnthe chamber, means for producinglongitudinal circulation through the material of the air within thechamber and means'for producing crosswise j circulation-of the airthrough the material a fat botliends' of the kiln. g

22'. A progressive dry kiln comprising an elongated chamber providedwith means for heating the air within the chamber, means go forproducing longitudinal circulation of the v air within the-chamberthrough the material therein, and means for producing crosswisecirculation through the material at one end Of the chamber; a g 23. In adry kiln, in combination, a heating chamber, means for developingself-controlled air recirculation actuated by diflerences in density ofpartially counterbalancing columnsof'hot and cold air, and means fordeveloping air recirculation independently of and crosswise of thefirst-mentioned circulation. 4

In testimony whereof, I have hereunto set my hand. a J. FORREST COBB.

